Free · Mathematical relationships

Right Triangle Area from Legs or an Angle

A right triangle has perpendicular legs a and b, a hypotenuse c and complementary acute angles. Its area is half the product of the legs.

Formula & worked example
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Formula and method

With given = 0, side_a1 = 3, side_b1 = 4, area1 = 6, side_c1 = 5.

A = ab/2; c² = a²+b²

Worked example

Enter these known values and leave the other values blank.

Given: 0
a: 3 cm
b: 4 cm

c: 5 cm
Area: 6 cm²

Assumptions and limitations

A right triangle has perpendicular legs a and b, a hypotenuse c and complementary acute angles. Its area is half the product of the legs.
Enter enough independent values and clear the quantity being solved. Locks preserve known values; contradictory inputs can make the system inconsistent. Unit controls convert physical quantities rather than merely changing their labels.
Displayed precision is numerical rounding, not an estimate of measurement uncertainty.

Common questions

How do I solve for a missing quantity?

Clear the missing value, enter the independent known values and retain compatible units. A nonunique inverse may require another known value.

What relationship is used?